1. Field of the Invention
The present invention relates to touch panels and, particularly, to a carbon nanotube based touch panel and a display device using the same.
2. Discussion of Related Art
Following the advancement in recent years of various electronic apparatuses, such as mobile phones, car navigation systems and the like, toward high performance and diversification, there has been continuous growth in the number of electronic apparatuses equipped with optically transparent touch panels at the front of their respective display devices (e.g., liquid crystal panels). A user of any such electronic apparatus operates it by pressing or touching the touch panel with a finger, a pen, stylus, or another like tool while visually observing the display device through the touch panel. Therefore, a demand exists for touch panels that provide superior visibility and reliable operation.
Up to the present time, different types of touch panels, including resistance, capacitance, infrared, and surface sound-wave types have been developed. The capacitance-type touch panel has advantages such as high accuracy and excellent transparency, thus has been widely used.
There are two types of conventional capacitance-type touch panels: single-point capacitance-type touch panel, and multipoint capacitance-type touch panel. The multipoint capacitance-type touch panel includes a driving layer and a sensing layer. The driving layer includes a plurality of driving lines parallel to each other. The sensing layer includes a plurality of sensing lines parallel to each other. The multipoint capacitance-type touch panel further includes a insulating layer disposed between the sensing layer and the driving layer. The sensing lines and the driving lines are arranged in different planes, and the orientation of the sensing lines is perpendicular to the orientation of the driving lines. Where projections of the sensing lines intersect with the driving lines form a plurality of capacitive sensing nodes. The sensing nodes represent different coordinates on the touch panel. The driving layer is connected to a driving circuit. The driving circuit separately and alternately drives a current through each of the driving lines while all the other lines are grounded. The sensing layer is connected to a capacitive sensing circuit. The capacitive sensing circuit continuously senses the capacitance of each of the sensing lines.
In operation, an upper surface of the touch panel is pressed/touched with one or several touch tools, such as an electrical pen or user's fingers. And visual observation of a screen on the liquid crystal display device provided on a backside of the touch panel is provided. In use, due to an electrical field of the user, coupling capacitances between the user's fingers and the sensing nodes disturb coupling capacitances between the first conductive lines and the second conductive lines. Thus, the touch tool takes away currents from the touch points. Currents flowing through the capacitive sensing circuit cooperatively replace the currents lost at the sensing nodes. The positions of the touch points can be simultaneously identified by an integrated circuit of the capacitive sensing circuit.
The material of the insulating layer is glass. The material of the driving lines and the sensing lines is selected from a group consisting of indium tin oxide (ITO) and antimony tin oxide (ATO). Additionally, a filling layer is formed in gaps between the adjacent lines. The material of the filling layer has similar refractive index as the material of the lines. As such, the touch panel with the filling layer can provide a uniform transparency.
The sensing lines and the driving lines (e.g., ITO lines) are generally formed by means of ion-beam sputtering, and this method is relatively complicated. Furthermore, the ITO lines have generally poor mechanical durability, low chemical endurance, and uneven resistance over an entire area of the touch panel. Additionally, the ITO layers have relatively low transparency. All the above-mentioned problems of the ITO layers tend to yield a touch panel with somewhat low sensitivity, accuracy, and brightness.
What is needed, therefore, is to provide a touch panel and a display device using the same having good durability, high sensitivity, accuracy, and brightness.